cmd/internal/objabi: assume GOARM=7 on Android

CL 34641 changed the Go runtime to assume GOARM=7 support on Android.
This change completes that by assuming GOARM=7 in the toolchain, fixing
the gotcha of inexplicably slow performance on non-arm64 Android devices.

There is already code in cmd/dist to force GOARM to 7 on GOOS=android. However,
dist is most likely run with GOOS != android.

Change-Id: I5e2bf11c3ecd0f6c193229eaa8ddc570722799d1
Reviewed-on: https://go-review.googlesource.com/c/go/+/272846
Run-TryBot: Elias Naur <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Cherry Zhang <[email protected]>
Trust: Elias Naur <[email protected]>

Author: eliasnaur

src/cmd/dist/util.go

@@ -383,12 +383,6 @@ func xsamefile(f1, f2 string) bool {
 }
 
 func xgetgoarm() string {
-	if goos == "android" {
-		// Assume all android devices have VFPv3.
-		// These ports are also mostly cross-compiled, so it makes little
-		// sense to auto-detect the setting.
-		return "7"
-	}
 	if gohostarch != "arm" || goos != gohostos {
 		// Conservative default for cross-compilation.
 		return "5"

src/cmd/internal/objabi/util.go

@@ -40,7 +40,12 @@ const (
 )
 
 func goarm() int {
-	switch v := envOr("GOARM", defaultGOARM); v {
+	def := defaultGOARM
+	if GOOS == "android" {
+		// Android devices always support GOARM=7.
+		def = "7"
+	}
+	switch v := envOr("GOARM", def); v {
 	case "5":
 		return 5
 	case "6":